<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>天气案例_监视属性</title>
  <!-- 引入Vue -->
  <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>
  <!-- 准备好一个容器 -->
  <div id="root">
    <h2>今天天气很{{info}}</h2>
    <button @click="changeWeather">切换天气</button>
    <hr />
    <h3>a的值是:{{numbers.a}}</h3>
    <button @click="numbers.a++">点我让a+1</button>
    <h3>b的值是:{{numbers.b}}</h3>
    <button @click="numbers.b++">点我让b+1</button>
    {{numbers.c.d.e}}
  </div>
</body>

<script type="text/javascript">

  const vm = new Vue({
    el: '#root',
    data: {
      isHot: true,
      numbers: {
        a: 1,
        b: 1,
        c: {
          d: {
            e: 100
          }
        }
      }
    },
    computed: {
      info() {
        return this.isHot ? '炎热' : '凉爽'
      }
    },
    methods: {
      changeWeather() {
        this.isHot = !this.isHot
      }
    },
    watch: {
      isHot: {
        // immediate: true, //初始化时让handler调用一下
        //handler什么时候调用？当isHot发生改变时
        handler(newValue, oldValue) {
          console.log('isHot被修改了', newValue, oldValue);
        }
      },
      //监视多级结构中某个属性的变化
      // 'numbers.a': {
      //   handler() {
      //     console.log('a被改变了');
      //   }
      // }

      //监视多级结构所有属性的变化
      numbers: {
        deep: true,
        handler() {
          console.log('numbers被改变了');
        }
      }

    }
  })
</script>

</html>